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Indiana University Studies 
volves a wheeleri x pezomachoides cross in the Cumberland 
Highlands and the Appalachian areas of central and eastern 
Tennessee, North Carolina, northern Georgia, and the borders 
of adjacent states in the South. Individuals that are certainly 
hybrids between wheeleri and pezomachoides are common 
from northern New England to Georgia wherever wheeleri 
still comes into contact with pezomachoides . Such hybrid 
individuals may be interpreted with much certainty and they 
confirm our explanation of advena in the Southern Highlands. 
The unusual amount of variation, the occurrence of segre- 
gates that appear as pure wheeleri or pure pezomachoides, 
and the geographic position of the hybrid between the sup- 
posed parents is, as with erinacei, the basis for recognizing 
the origin of advena. Segregates of wheeleri are more 
common in advena than in erinacei, probably because advena 
is not yet free from current contributions from the nearly 
pure populations of wheeleri which occur in the southern 
mountains. The galls of advena are interesting because they 
run largely to the smooth form typical of pezomachoides, indi- 
cating some dominance of pezomachoides characters ; but 
advena galls are very finely bristly, and large series do in- 
clude a few that are as strictly spiny as those of wheeleri. 
We have then, out of the 93 species in the genus, the follow- 
ing which we would recognize as of hybrid origin : 
C. fulvicollis ( — C. canadensis x major) 
C. gemmula ( = C. suspecta x fuscata?) 
C. erinacei ( = C. wheeleri x derivatus) 
C. advena ( = C. wheeleri x pezomachoides) 
C. macrescens (=C. scelesta x opima) 
